1. Field of the Invention
The invention concerns a method and apparatus for gripping parcels the nature of which makes handling them by traditional means awkward, and more specifically, the invention is designed for handling parcels which readily change shape, in particular when subjected to mechanical pressure, which are large in size, and which are relatively fragile.
2. Description of the Prior Art
The handling of parcels containing products such as fiberglass wool padding poses quite special problems relating to the dimensions, fragility, and capacity for deformation of such parcels.
In most normal circumstances, fiberglass padding used for insulation purposes is produced in rolls as wide as, or even wider than, 1.20 m and with a diameter of 0.60 m, for example, or perhaps in groups of panels making up a parallelepiped-shaped parcel 1.20 m long and measuring 0.6 m by 0.6 m in its other dimensions. Such parcels, it is clear, are relatively bulky. Moreover, they have a low/mass volume ratio ranging from about 15 kg/m.sup.3 to 100 kg/m.sup.3, with the result being that a typical roll, as described above, would weigh from 8 kg to 30 kg.
The parcels in question are further distinguished by the fact that their packaging is relatively fragile. The packaging ordinarily consists in a sheet of a macromolecular material, perhaps shrunken, such as sheets of polyvinyl chloride, polyethylene, polypropylene or analogous materials, or sheets of relatively strong paper.
This light packaging has the advantage of being relatively inexpensive, but it protects the product only marginally against deformation or tearing which can result from poorly adapted handling procedures. Accordingly, the packaging contributes to the poorly defined and rounded geometrical forms of the parcels.
Even if an effort is made to process fiberglass-based products continuously on the production line, going directly from fiber-making all the way to final packaging and thereby avoiding transfer operations, it is necessary at the end of the sequence to gather the wrapped products and take them to storage points, usually on pallets or wagons. It is quite difficult to use traditional gripping devices such as hooks, pincers, etc., for placing these goods on pallets because of the susceptibility of the packaging to piercing and the low resistance of the products to crushing. For this reason, the pallets are often loaded manually, a process which is neither satisfactory nor very rational from an economic viewpoint.